Optical coatings are thin films of material deposited in layers onto lenses for tuning their optical properties, usually light reflectance and transmission, to suit the lenses' intended purpose. The thickness and composition of these coatings, amongst other parameters, determine the resultant physical effects on the lenses' optical profile. In the eyeglass lens industry, optical coatings are applied for purposes such as anti-reflectance, scratch resistance, high-reflectance in sunglasses, ease of cleaning, anti-fog or other benefits.
A common feature in modern eyeglass lens manufacturing are anti-reflective (AR) coatings. An AR coating is typically achieved via deposition of thin layers of materials that in combination severely limit the reflection of visible light off the lens thus increasing the transmission of visible light through the lens. AR-coated lenses allow approximately 98% to as much as over 99% transmission of light through the lens, whereas some non-AR coated lenses may allow only 92% transmission of light through the lens. These coatings are popular because, in addition to improved visible light transmission, they offer numerous other benefits such as decreased surface reflections, glare, and ghost images. Currently, there are several different processes for generating lenses with such properties; each of these methods yields distinct physical properties, quality, and longevity of the end product.